UcD400 Q & A

[Bruno Putzeys]

Originally posted by Lou Cipher
I read somwhere(i guess this forum) that the Ucd400 has a rather low current limiter compared to the Zappulse which cuts at 25A.

The UcD400 starts protecting around 20Amps. The UcD700 will cut off at around 28A.

I get the impression that virtual maximum currents mean more to you than actual audio performance. Have you ever seen such currents in your system? 25A at 60V corresponds to 750Wrms into 2.4 ohms. Do your speakers have such an impedance minimum? I know that many amplifier designs can only deliver good performance at listening levels by having huge unused "reserves" (=using a smaller and hence more linear fraction of the output characteristic). It is manufacturers of such amplifiers who perpetuate the high current myth to hide the fact that their amplifiers actually have a problem. Other amplifiers deliver flawless performance right up to the point when they protect or clip. With such amplifiers it is simply unnecessary to have more current capability on hand than you will ever need. For that reason, how much unused current capability an amplifier has is a useless metric.

[Jan-Peter]

Originaly posted Lou Cipher;
Yea I know, I know....

I'ts just that the more you read the more confused you get and then you start looking at details As a teatcher of mine once said: "Still confused but at a higher level"

Having touble deciding which one to go for. Ucd400 do has an price advantage.

Did you checked this measurement in 4 ohm?

Jan-Peter

[Bruno Putzeys]

Originally posted by Tarasque
Iam wondering if the UCD400 modules in bridged mode would also cancel out some of the distorsion products?

At the same time I would like to know how the modules could best connected.

my speaker has a wide impedance range, from 3 - 19 Ohm. Would bridge mode operation (42V supply) be able to handle 3 Ohm?

Bridge connection only removes odd distortion components. The UcD modules don't have much odd harmonics, so bridging will not produce a performance advantage.

If your speakers go down to 3 ohms, it's better to run your amps at 60V and not to bridge them. Bridging is only useful if your speakers have a higher impedance (e.g. 6 ohms minimum). Of course if you have only 42V, bridging will increase power even with 3 ohms.

[JohnW]

Hi Bruno,

I'm sure you meant to say Even order....



John

[Lou Cipher]

Originally posted by Bruno Putzeys
I get the impression that virtual maximum currents mean more to you than actual audio performance.

No. Audio performance is my main objective i.e. neutral and transparent sound. It was just a question from my side.

Thanks Jan-Peter for the chart.

[Bruno Putzeys]

Originally posted by JohnW
Hi Bruno,

I'm sure you meant to say Even order....



John

Yer right dammit

[JohnW]

Yep - didn't our friends at NASA get the focal length of the Hubble telescope wrong - and just recently crash a billion dollar craft into the surface of Mars due to a mix-up over metric and imperial units...

I sure wish that we could cancel odd order with bridging – bloody phase shift….

John

[ewildgoose]

Originally posted by Bruno Putzeys

I know that many amplifier designs can only deliver good performance at listening levels by having huge unused "reserves" (=using a smaller and hence more linear fraction of the output characteristic). It is manufacturers of such amplifiers who perpetuate the high current myth to hide the fact that their amplifiers actually have a problem. Other amplifiers deliver flawless performance right up to the point when they protect or clip. With such amplifiers it is simply unnecessary to have more current capability on hand than you will ever need. For that reason, how much unused current capability an amplifier has is a useless metric.

I think I have an interesting example of this. I have been doing a lot of experimentation with DSP correction of the audio, and getting really good results. Have a look here for some details on the state of the art right now:

http://www.duffroomcorrection.com

However, in the early days I was using a Meridian 557 power amp, which I think is fairly reasonable as hifi kit goes. With lots of correction, ie 6dB or so, all the dynamics tended to disappear from the sound. It sounded "good", but boring. (And of course this means I just lost 3/4 of my amp power by definition)

This was what started me looking at the switching amps, and since adding in my Zappulse and UCD amps I find that the speakers are driven effortlessly. I still find turning up the volume increases distortion too quickly (Proac 1.5 I can't quite run them at disco levels...), but I think this is speaker issues not amp issues. Actually, I added a serious IB system to cover the bass area and you can now hear how effortless the bass is at high volumes, so next step is to build some much more dynamic speakers.

I haven't listened to very many seriously high end amps, ie north of £4K. But the few I have suggest to me that they aren't a world ahead of the UCD400, if at all. Personally I strive for a very dynamic sound so I don't even find that many of these expensive amps do what I want anyway, and I think I will be happier with a bank of "cheap" active UCD400 designs than I will be with a single stereo high end (passive crossover) traditional design. This is at least my current design path... We will see...

[Lou Cipher]

What S/N ratio does the Ucd400 have?

Isn't there a more detailed spec of this module available?

[Bruno Putzeys]

My recent career move will allow more time to write a proper spec

The specs of the UcD400 and UcD180 modules are very much the same except for the higher output capability. The output noise level is about 20uV rms unweighted (20Hz-20kHz). Referred to 400W into 4 ohms that's about 126dB or 100dB re 1W/4R